class MVVM {
  constructor(opt) {
    this.$el = opt.el;
    this.$data = opt.data;

    if (this.$el) {
      //数据劫持
      new Observer(this.$data);

      //模板编译
      new Compile(this.$el, this.$data);

      //监听数据
      // new Watcher(this.$el, this.$data)

    }
  }
}